In recent years, various wireless communication systems, especially wireless communication systems of cellular network architectures, have been developed continuously due to the rapid development of wireless communication technologies so as to satisfy various communication demands and applications in people's daily life. A Narrowband Internet of Things (NB-IoT) system is one of the wireless communication systems developed in recent years, and it mainly aims at user equipments (UEs) characterized by low power consumption, low complexity, low cost, high transmission delay tolerance, or the like, so it has become the wireless communication system most actively developed currently for IoT devices.
In currently existing NB-IoT systems, in order to enable downlink control information (DCI) to be transmitted to UEs around cell edge of a base station, the base station repeats the transmission of the DCI so as to improve the possibility of successfully decoding the data at the UE end.
In detail, the base station configures the DCI subframe repetition number in a narrowband physical downlink control channel (NPDCCH) according to a coverage enhancement level (CE Level) where the UE is located. However, the DCI subframe repetition number is configured for all UEs in each of the CE levels, so the base station performs the radio resource scheduling and allocation based on the same DCI subframe repetition number for all the UEs at a same CE level. For example, if the CE levels are divided into three levels and the DCI subframe repetition numbers corresponding to the three levels are respectively configured to be 2, 4, and 8, then the base station allocates the subframe at the DCI subframe repetition number corresponding to the CE level where the UE is located, thereby transmitting the downlink control information to the UE.
However, for the UE near the base station and thus performing well in receiving signals, even if the number of continuous subframes required by the UE for correctly decoding the DCI is less than the corresponding DCI subframe repetition number (e.g., the configured DCI subframe repetition number is 4, but actually the UE can correctly decode the DCI simply by receiving the DCI repeatedly transmitted in 2 continuous subframes), the base station still transmits the DCI repeatedly by using continuous subframes corresponding to the configured DCI subframe repetition number in the current radio resource allocation mechanism. In other words, the base station in the prior art configures the DCI subframe repetition number only based on the CE levels instead of configuring the DCI subframe repetition number based on individual UEs (especially the individual UEs in a same CE level). In this case, since the NPDCCH radio resources configured are limited, even if the narrowband physical downlink share channel (NPDSCH) or the narrowband physical uplink share channel (NPUSCH) still have radio resources to be allocated, the base station still cannot allocate the NPDSCH radio resources or the NPUSCH radio resources remaining unallocated to other UEs because no radio resource is available for allocation in the NPDCCH to transmit DCI of other UEs.
For example, as shown in FIG. 1, if the NPDCCH radio resources configured in each NPDCCH period are 16 subframes, then for the UEs whose DCI subframe repetition number configured corresponding to the CE level is 4, the NPDCCH radio resources can only be allocated to four UEs at the CE level. In this case, even if the NPDSCH still have radio resources to be allocated in the same NPDCCH period, the base station still cannot allocate the NPDSCH radio resources remaining unallocated to a fifth UE, or the base station cannot allocate the corresponding NPUSCH radio resources to the fifth UE in the NPDCCH period. Accordingly, the current radio resource allocation mechanism cannot optimize the radio resource scheduling and allocation to serve more UEs with the limited radio resources.
Accordingly, an urgent need exists in the art to provide a radio resource allocation mechanism so as to serve more UEs with the limited radio resources, thereby preventing the waste of the radio resources, and thus improving the utilization ratio of the radio resources, the total throughput capacity of the system, and the resource scheduling flexibility.